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# ATCNet
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ATCNet from Altaheri et al (2022) .
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> **Architecture-only repository.**
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> `braindecode.models.ATCNet` class. **No pretrained weights are
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> distributed here**
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> data
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> separately.
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## Quick start
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The signal-shape arguments above are
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## Documentation
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<https://braindecode.org/stable/generated/braindecode.models.ATCNet.html>
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- Interactive browser with live instantiation:
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<https://huggingface.co/spaces/braindecode/model-explorer>
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- Source on GitHub: <https://github.com/braindecode/braindecode/blob/master/braindecode/models/atcnet.py#L15>
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## Architecture description
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The block below is the rendered class docstring (parameters,
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references, architecture figure where available).
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<div class='bd-doc'><main>
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<p>ATCNet from Altaheri et al (2022) [1]_.</p>
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<span style="display:inline-block;padding:2px 8px;border-radius:4px;background:#5cb85c;color:white;font-size:11px;font-weight:600;margin-right:4px;">Convolution</span><span style="display:inline-block;padding:2px 8px;border-radius:4px;background:#6c757d;color:white;font-size:11px;font-weight:600;margin-right:4px;">Recurrent</span><span style="display:inline-block;padding:2px 8px;border-radius:4px;background:#56B4E9;color:white;font-size:11px;font-weight:600;margin-right:4px;">Attention/Transformer</span>
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.. figure:: https://user-images.githubusercontent.com/25565236/185449791-e8539453-d4fa-41e1-865a-2cf7e91f60ef.png
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:align: center
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:alt: ATCNet Architecture
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:width: 650px
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.. rubric:: Architectural Overview
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ATCNet is a *convolution-first* architecture augmented with a *lightweight attention–TCN*
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sequence module. The end-to-end flow is:
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- (i) :class:`_ConvBlock` learns temporal filter-banks and spatial projections (EEGNet-style),
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downsampling time to a compact feature map;
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- (ii) Sliding Windows carve overlapping temporal windows from this map;
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- (iii) for each window, :class:`_AttentionBlock` applies small multi-head self-attention
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over time, followed by a :class:`_TCNResidualBlock` stack (causal, dilated);
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- (iv) window-level features are aggregated (mean of window logits or concatenation)
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and mapped via a max-norm–constrained linear layer.
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Relative to ViT, ATCNet replaces linear patch projection with learned *temporal–spatial*
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convolutions; it processes *parallel* window encoders (attention→TCN) instead of a deep
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stack; and swaps the MLP head for a TCN suited to 1-D EEG sequences.
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.. rubric:: Macro Components
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- :class:`_ConvBlock` **(Shallow conv stem → feature map)**
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- *Operations.*
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- **Temporal conv** (:class:`torch.nn.Conv2d`) with kernel ``(L_t, 1)`` builds a
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FIR-like filter bank (``F1`` maps).
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- **Depthwise spatial conv** (:class:`torch.nn.Conv2d`, ``groups=F1``) with kernel
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``(1, n_chans)`` learns per-filter spatial projections (akin to EEGNet's CSP-like step).
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- **BN → ELU → AvgPool → Dropout** to stabilize and condense activations.
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- **Refining temporal conv** (:class:`torch.nn.Conv2d`) with kernel ``(L_r, 1)`` +
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**BN → ELU → AvgPool → Dropout**.
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The output shape is ``(B, F2, T_c, 1)`` with ``F2 = F1·D`` and ``T_c = T/(P1·P2)``.
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Temporal kernels behave as FIR filters; the depthwise-spatial conv yields frequency-specific
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topographies. Pooling acts as a local integrator, reducing variance and imposing a
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useful inductive bias on short EEG windows.
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- **Sliding-Window Sequencer**
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From the condensed time axis (length ``T_c``), ATCNet forms ``n`` overlapping windows
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of width ``T_w = T_c - n + 1`` (one start per index). Each window produces a sequence
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``(B, F2, T_w)`` forwarded to its own attention-TCN branch. This creates *parallel*
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encoders over shifted contexts and is key to robustness on nonstationary EEG.
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- :class:`_AttentionBlock` **(small MHA on temporal positions)**
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Attention here is *local to a window* and purely temporal.
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- *Operations.*
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- Rearrange to ``(B, T_w, F2)``,
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- Normalization :class:`torch.nn.LayerNorm`
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- Custom MultiHeadAttention :class:`_MHA` (``num_heads=H``, per-head dim ``d_h``) + residual add,
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- Dropout :class:`torch.nn.Dropout`
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- Rearrange back to ``(B, F2, T_w)``.
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*Role.* Re-weights evidence across the window, letting the model emphasize informative
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segments (onsets, bursts) before causal convolutions aggregate history.
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- :class:`_TCNResidualBlock` **(causal dilated temporal CNN)**
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*Operations:*
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- Two :class:`braindecode.modules.CausalConv1d` layers per block with dilation ``1, 2, 4, …``
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- Across blocks of `torch.nn.ELU` + `torch.nn.BatchNorm1d` + `torch.nn.Dropout`) +
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a residual (identity or 1x1 mapping).
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- The final feature used per window is the *last* causal step ``[..., -1]`` (forecast-style).
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*Role.* Efficient long-range temporal integration with stable gradients; the dilated
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receptive field complements attention's soft selection.
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- **Aggregation & Classifier**
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*Operations:*
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- Either (a) map each window feature ``(B, F2)`` to logits via :class:`braindecode.modules.MaxNormLinear`
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and **average** across windows (default, matching official code), or
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- (b) **concatenate** all window features ``(B, n·F2)`` and apply a single :class:`MaxNormLinear`.
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The max-norm constraint regularizes the readout.
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.. rubric:: Convolutional Details
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- **Temporal.** Temporal structure is learned in three places:
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- (1) the stem's wide ``(L_t, 1)`` conv (learned filter bank),
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- (2) the refining ``(L_r, 1)`` conv after pooling (short-term dynamics), and
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- (3) the TCN's causal 1-D convolutions with exponentially increasing dilation
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(long-range dependencies). The minimum sequence length required by the TCN stack is
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``(K_t - 1)·2^{L-1} + 1``; the implementation *auto-scales* kernels/pools/windows
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when inputs are shorter to preserve feasibility.
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- **Spatial.** A depthwise spatial conv spans the **full montage** (kernel ``(1, n_chans)``),
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producing *per-temporal-filter* spatial projections (no cross-filter mixing at this step).
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This mirrors EEGNet's interpretability: each temporal filter has its own spatial pattern.
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.. rubric:: Attention / Sequential Modules
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- **Type.** Multi-head self-attention with ``H`` heads and per-head dim ``d_h`` implemented
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in :class:`_MHA`, allowing ``embed_dim = H·d_h`` independent of input and output dims.
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- **Shapes.** ``(B, F2, T_w) → (B, T_w, F2) → (B, F2, T_w)``. Attention operates along
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the **temporal** axis within a window; channels/features stay in the embedding dim ``F2``.
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- **Role.** Highlights salient temporal positions prior to causal convolution; small attention
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keeps compute modest while improving context modeling over pooled features.
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.. rubric:: Additional Mechanisms
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- **Parallel encoders over shifted windows.** Improves montage/phase robustness by
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ensembling nearby contexts rather than committing to a single segmentation.
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- **Max-norm classifier.** Enforces weight norm constraints at the readout, a common
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stabilization trick in EEG decoding.
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- **ViT vs. ATCNet (design choices).** Convolutional *nonlinear* projection rather than
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linear patchification; attention followed by **TCN** (not MLP); *parallel* window
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encoders rather than stacked encoders.
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.. rubric:: Usage and Configuration
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- ``conv_block_n_filters (F1)``, ``conv_block_depth_mult (D)`` → capacity of the stem
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(with ``F2 = F1·D`` feeding attention/TCN), dimensions aligned to ``F2``, like :class:`EEGNet`.
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- Pool sizes ``P1,P2`` trade temporal resolution for stability/compute; they set
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``T_c = T/(P1·P2)`` and thus window width ``T_w``.
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- ``n_windows`` controls the ensemble over shifts (compute ∝ windows).
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- ``num_heads``, ``head_dim`` set attention capacity; keep ``H·d_h ≈ F2``.
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- ``tcn_depth``, ``tcn_kernel_size`` govern receptive field; larger values demand
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longer inputs (see minimum length above). The implementation warns and *rescales*
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kernels/pools/windows if inputs are too short.
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- **Aggregation choice.** ``concat=False`` (default, average of per-window logits) matches
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the official code; ``concat=True`` mirrors the paper's concatenation variant.
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Parameters
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----------
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input_window_seconds : float, optional
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Time length of inputs, in seconds. Defaults to 4.5 s, as in BCI-IV 2a
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dataset.
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sfreq : int, optional
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Sampling frequency of the inputs, in Hz. Default to 250 Hz, as in
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BCI-IV 2a dataset.
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conv_block_n_filters : int
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Number temporal filters in the first convolutional layer of the
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convolutional block, denoted F1 in figure 2 of the paper [1]_. Defaults
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to 16 as in [1]_.
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conv_block_kernel_length_1 : int
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Length of temporal filters in the first convolutional layer of the
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convolutional block, denoted Kc in table 1 of the paper [1]_. Defaults
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to 64 as in [1]_.
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conv_block_kernel_length_2 : int
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Length of temporal filters in the last convolutional layer of the
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convolutional block. Defaults to 16 as in [1]_.
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conv_block_pool_size_1 : int
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Length of first average pooling kernel in the convolutional block.
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Defaults to 8 as in [1]_.
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conv_block_pool_size_2 : int
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Length of first average pooling kernel in the convolutional block,
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denoted P2 in table 1 of the paper [1]_. Defaults to 7 as in [1]_.
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conv_block_depth_mult : int
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Depth multiplier of depthwise convolution in the convolutional block,
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denoted D in table 1 of the paper [1]_. Defaults to 2 as in [1]_.
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conv_block_dropout : float
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Dropout probability used in the convolution block, denoted pc in
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table 1 of the paper [1]_. Defaults to 0.3 as in [1]_.
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n_windows : int
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Number of sliding windows, denoted n in [1]_. Defaults to 5 as in [1]_.
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head_dim : int
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Embedding dimension used in each self-attention head, denoted dh in
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table 1 of the paper [1]_. Defaults to 8 as in [1]_.
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num_heads : int
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Number of attention heads, denoted H in table 1 of the paper [1]_.
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Defaults to 2 as in [1]_.
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att_dropout : float
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Dropout probability used in the attention block, denoted pa in table 1
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of the paper [1]_. Defaults to 0.5 as in [1]_.
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tcn_depth : int
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Depth of Temporal Convolutional Network block (i.e. number of TCN
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Residual blocks), denoted L in table 1 of the paper [1]_. Defaults to 2
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as in [1]_.
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tcn_kernel_size : int
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Temporal kernel size used in TCN block, denoted Kt in table 1 of the
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paper [1]_. Defaults to 4 as in [1]_.
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tcn_dropout : float
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Dropout probability used in the TCN block, denoted pt in table 1
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of the paper [1]_. Defaults to 0.3 as in [1]_.
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tcn_activation : torch.nn.Module
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Nonlinear activation to use. Defaults to nn.ELU().
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concat : bool
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When ``True``, concatenates each slidding window embedding before
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feeding it to a fully-connected layer, as done in [1]_. When ``False``,
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maps each slidding window to `n_outputs` logits and average them.
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Defaults to ``False`` contrary to what is reported in [1]_, but
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matching what the official code does [2]_.
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max_norm_const : float
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Maximum L2-norm constraint imposed on weights of the last
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fully-connected layer. Defaults to 0.25.
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Notes
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-----
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- Inputs substantially shorter than the implied minimum length trigger **automatic
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downscaling** of kernels, pools, windows, and TCN kernel size to maintain validity.
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- The attention–TCN sequence operates **per window**; the last causal step is used as the
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window feature, aligning the temporal semantics across windows.
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.. versionadded:: 1.1
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- More detailed documentation of the model.
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References
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----------
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.. [1] H. Altaheri, G. Muhammad, M. Alsulaiman (2022).
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*Physics-informed attention temporal convolutional network for EEG-based motor imagery classification.*
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IEEE Transactions on Industrial Informatics. doi:10.1109/TII.2022.3197419.
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.. [2] Official EEG-ATCNet implementation (TensorFlow):
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https://github.com/Altaheri/EEG-ATCNet/blob/main/models.py
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.. rubric:: Hugging Face Hub integration
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When the optional ``huggingface_hub`` package is installed, all models
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automatically gain the ability to be pushed to and loaded from the
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Hugging Face Hub. Install with::
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pip install braindecode[hub]
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**Pushing a model to the Hub:**
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.. code::
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from braindecode.models import ATCNet
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# Train your model
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model = ATCNet(n_chans=22, n_outputs=4, n_times=1000)
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# ... training code ...
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# Push to the Hub
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model.push_to_hub(
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repo_id="username/my-atcnet-model",
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commit_message="Initial model upload",
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)
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**Loading a model from the Hub:**
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.. code::
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from braindecode.models import ATCNet
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# Load pretrained model
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model = ATCNet.from_pretrained("username/my-atcnet-model")
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# Load with a different number of outputs (head is rebuilt automatically)
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model = ATCNet.from_pretrained("username/my-atcnet-model", n_outputs=4)
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**Extracting features and replacing the head:**
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import torch
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# Extract encoder features (consistent dict across all models)
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out = model(x, return_features=True)
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features = out["features"]
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# Replace the classification head
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model.reset_head(n_outputs=10)
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config = model.get_config() # all __init__ params
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with open("config.json", "w") as f:
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json.dump(config, f)
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saved to the Hub and restored when loading.
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See :ref:`load-pretrained-models` for a complete tutorial.</main>
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</div>
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## Citation
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*References* section above) and braindecode:
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```bibtex
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@article{aristimunha2025braindecode,
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# ATCNet
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ATCNet from Altaheri et al (2022) [1].
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> **Architecture-only repository.** Documents the
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> `braindecode.models.ATCNet` class. **No pretrained weights are
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> distributed here.** Instantiate the model and train it on your own
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> data.
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## Quick start
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)
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```
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The signal-shape arguments above are illustrative defaults — adjust to
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match your recording.
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## Documentation
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+
- Full API reference: <https://braindecode.org/stable/generated/braindecode.models.ATCNet.html>
|
| 46 |
+
- Interactive browser (live instantiation, parameter counts):
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| 47 |
<https://huggingface.co/spaces/braindecode/model-explorer>
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| 48 |
- Source on GitHub: <https://github.com/braindecode/braindecode/blob/master/braindecode/models/atcnet.py#L15>
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| 49 |
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| 50 |
|
| 51 |
+
## Architecture
|
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|
| 52 |
|
| 53 |
+

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|
| 54 |
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|
| 55 |
|
| 56 |
+
## Parameters
|
| 57 |
|
| 58 |
+
| Parameter | Type | Description |
|
| 59 |
+
|---|---|---|
|
| 60 |
+
| `input_window_seconds` | float, optional | Time length of inputs, in seconds. Defaults to 4.5 s, as in BCI-IV 2a dataset. |
|
| 61 |
+
| `sfreq` | int, optional | Sampling frequency of the inputs, in Hz. Default to 250 Hz, as in BCI-IV 2a dataset. |
|
| 62 |
+
| `conv_block_n_filters` | int | Number temporal filters in the first convolutional layer of the convolutional block, denoted F1 in figure 2 of the paper [1]. Defaults to 16 as in [1]. |
|
| 63 |
+
| `conv_block_kernel_length_1` | int | Length of temporal filters in the first convolutional layer of the convolutional block, denoted Kc in table 1 of the paper [1]. Defaults to 64 as in [1]. |
|
| 64 |
+
| `conv_block_kernel_length_2` | int | Length of temporal filters in the last convolutional layer of the convolutional block. Defaults to 16 as in [1]. |
|
| 65 |
+
| `conv_block_pool_size_1` | int | Length of first average pooling kernel in the convolutional block. Defaults to 8 as in [1]. |
|
| 66 |
+
| `conv_block_pool_size_2` | int | Length of first average pooling kernel in the convolutional block, denoted P2 in table 1 of the paper [1]. Defaults to 7 as in [1]. |
|
| 67 |
+
| `conv_block_depth_mult` | int | Depth multiplier of depthwise convolution in the convolutional block, denoted D in table 1 of the paper [1]. Defaults to 2 as in [1]. |
|
| 68 |
+
| `conv_block_dropout` | float | Dropout probability used in the convolution block, denoted pc in table 1 of the paper [1]. Defaults to 0.3 as in [1]. |
|
| 69 |
+
| `n_windows` | int | Number of sliding windows, denoted n in [1]. Defaults to 5 as in [1]. |
|
| 70 |
+
| `head_dim` | int | Embedding dimension used in each self-attention head, denoted dh in table 1 of the paper [1]. Defaults to 8 as in [1]. |
|
| 71 |
+
| `num_heads` | int | Number of attention heads, denoted H in table 1 of the paper [1]. Defaults to 2 as in [1]. |
|
| 72 |
+
| `att_dropout` | float | Dropout probability used in the attention block, denoted pa in table 1 of the paper [1]. Defaults to 0.5 as in [1]. |
|
| 73 |
+
| `tcn_depth` | int | Depth of Temporal Convolutional Network block (i.e. number of TCN Residual blocks), denoted L in table 1 of the paper [1]. Defaults to 2 as in [1]. |
|
| 74 |
+
| `tcn_kernel_size` | int | Temporal kernel size used in TCN block, denoted Kt in table 1 of the paper [1]. Defaults to 4 as in [1]. |
|
| 75 |
+
| `tcn_dropout` | float | Dropout probability used in the TCN block, denoted pt in table 1 of the paper [1]. Defaults to 0.3 as in [1]. |
|
| 76 |
+
| `tcn_activation` | torch.nn.Module | Nonlinear activation to use. Defaults to nn.ELU(). |
|
| 77 |
+
| `concat` | bool | When `True`, concatenates each slidding window embedding before feeding it to a fully-connected layer, as done in [1]. When `False`, maps each slidding window to `n_outputs` logits and average them. Defaults to `False` contrary to what is reported in [1], but matching what the official code does [2]. |
|
| 78 |
+
| `max_norm_const` | float | Maximum L2-norm constraint imposed on weights of the last fully-connected layer. Defaults to 0.25. |
|
| 79 |
|
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|
| 80 |
|
| 81 |
+
## References
|
| 82 |
|
| 83 |
+
1. H. Altaheri, G. Muhammad, M. Alsulaiman (2022). *Physics-informed attention temporal convolutional network for EEG-based motor imagery classification.* IEEE Transactions on Industrial Informatics. doi:10.1109/TII.2022.3197419.
|
| 84 |
+
2. Official EEG-ATCNet implementation (TensorFlow): https://github.com/Altaheri/EEG-ATCNet/blob/main/models.py
|
|
|
|
| 85 |
|
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|
| 86 |
|
| 87 |
## Citation
|
| 88 |
|
| 89 |
+
Cite the original architecture paper (see *References* above) and braindecode:
|
|
|
|
| 90 |
|
| 91 |
```bibtex
|
| 92 |
@article{aristimunha2025braindecode,
|